The present invention relates broadly to marking or printing systems, and particularly to a method for marking the surface of objects with a sequence of indentation-defined or spray-marked segmented characters.
As industry has continued to refine and improve production techniques and procedures, corresponding requirements have been levied for placing machine readable identifying, data related markings upon components of manufactured components. With such marking, the history of a product may be traced throughout the stages of its manufacture and components of complex machinery such as automobiles and the like may be identified, for example, in the course of investigations by governmental authorities. The call for identification, however, not only is concerned with the application of sequential, alphanumeric strings to completed products, but also to component parts of fabrications such as automobiles and piece parts as they may progressing through an industrial process, and to tags which may be attached to these parts.
A variety of product marking approaches have been employed by industry. For example, laser etching and ink and paint spraying of codes, such as dot matrix or segmented characters, have been employed for many manufacturing processes. Where the production environment is too rigorous, however, or subsequent painting steps are involved, such an approach has been found to be unacceptable with more permanent markings being required. Use of lasers to mark the surface of products or other, painted surfaces, has generally failed to overcome these same concerns.
The provision of a permanent or traceable marking upon hard surfaces, such as metals, traditionally has been achieved with marking punches which utilize dies and carry a collection of fully formed characters. These "full face dies" may be positioned in a wheel or ball form of die carrier which is manipulated to define a necessarily short message as it is dynamically struck into the material to be marked. As is apparent, the necessarily complex mechanisms involved are prone to failure and full face dies exhibit rapid wear. Generally, the legibility and abrasion resistance of the resultant marks can be considered to be only fair in quality. Additionally, the marking punch approach is considered a poor performer in marking such surfaces as epoxy coatings and the like.
A technique that has been successful in the marketplace for generating permanent markings upon the surfaces of somewhat malleable materials such as metals and plastics is described by Robertson in commonly-assigned U.S. Pat. No. 4,506,999 entitled "Program Controlled Pin Matrix Embossing Apparatus." Such technique involves a computer controlled dot-matrix marking device utilizing an array of pneumatically-driven tool steel punches to generate human and/or machine readable dot characters or codes. Marketed commercially under the trade designation PINSTAMP.RTM., these devices employ one or more of the noted steel pins in a head assembly which is moved relative to the workpiece being marked to impart permanent dot-matrix characters or machine readable codes into a surface. The system enjoys the advantage of providing characters of good legibility as well as permanence. Additionally, a capability for directional formation of messages or codes is realized.
Robertson et al., in commonly-assigned U.S. Pat. No. 4,808,018, entitled "Marking Apparatus with Matrix Defining Locus of Movement", issued Feb. 28, 1989, describe a dot-matrix character impact marking apparatus which is capable of forming messages or arrays of characters within a very confined region. With this device, a linear array of marker pins is moved by a carriage in a manner defining a predetermined undulating pattern of movement in a vertical raster-type fashion resembling a compressed square wave. This pattern traces the matrix within which individual characters are formed by individual marker pins. Each marking pin within the head assembly of this device is capable of marking more than one complete character for a given traverse of the head between its limits of movement.
Robertson et al., in U.S. Pat. No. 5,015,106, issued May 14, 1991, and entitled "Marking Apparatus with Multiple Line Capability" describe a dot-matrix character impact marking apparatus which achieves a multiple line capability wherein a carriage component carrying one or more marker pin cartridges moves within a singular plane pattern of movement. This multiple line capability advantageously has permitted a broad variety of line configurations, for example in widely spaced positions at a workpiece. The device further employs a retrace method in generating a pattern of marking movement fixed in a predetermined pattern somewhat similar to the formation of a horizontal raster associated with television displays. As before, the device performs in conjunction with a predetermined character defining matrix of pixel positions, each position of the matrix being identified to the system by a timing disk physically maneuvered with the drive components. This apparatus is designed to print dot-matrix characters.
Robertson el al., in commonly-assigned U.S. Pat. No. 5,316,397, entitled "Marking Apparatus With Multiple Marking Modes", filed Jul. 31, 1992, describe a matrix form of character marking utilizing a single plane undulatory motion of the pin cartridge carrying carriage, as well as a capability for the above-described raster form of pattern of movement. This flexibility is achieved through the utilization of software changes as opposed to the insertion of hardware-based timing components and the like. The system disclosed exhibits a capability for full form character formation. This requires the actuation of the marker pins in a manner wherein discrete dots or pixels are not observable, the indentations formed by these pins being so closely nested as to evoke the image of a continuous line forming each character. This device is effective for generating segmented characters or character segments.
There are many human-readable fonts available, but they are have the disadvantage of being slow to print and difficult to recognize using machine readers. The machine reading of dot-matrix characters and codes following their formation may be carried out by a video based system described in U.S. Pat. No. 4,806,741, by Robertson, entitled "Electronic Code Enhancement for Code Readers", issued Feb. 21, 1989.
Certain marking applications of the dot-peen variety call for the use of a single marking pin as opposed to an array of pins. Guidance of this form of single pin typically has been carried out under robotic control. One such system currently is marketed under the trade designation "TMP 6000" by Telesis Technologies, Inc., of Circleville, Ohio, the original assignee of the present application.
Applying spray-marked segmented characters to products for identification purposes is well-known. U.S. Pat. No. 3,584,571, issued to Schmoll, discloses a character generation marking device comprised of a plurality of selectively-actuable spray nozzles mounted in a fixed, predetermined pattern for effecting the placement of line segments on an object. The apparatus disclosed by Schmoll is capable of marking segmented characters with the number of characters being limited to the number of spray nozzles employed. Furthermore, Schmoll requires a great deal of space in which to operate and is incapable of optimizing the path of the print nozzles during the print cycle since the nozzles are fixed in relation to the object being marked. Also, Schmoll neither suggests nor discloses the advantage of optimizing the path of the nozzles in order to speed up the printing cycle.
U.S. Pat. No. 4,218,971, issued to Uhl et al., also discloses an actuation system for a rotating print wheel for printing segmented characters onto moving objects, wherein a rotating print cylinder, housing seven actuable segments, attracts ink from a stationary ink cartridge for transference to said object. However, since the segments are fixed on a print drum, there is no provision for optimizing the movement of the drum based upon the number of segments, i.e., the particular character or character string being printed. Since the movement of the print drum is not alterable based on the characters being printed, the print cycle from one character string to another will not vary. Like Schmoll, Uhl et al. requires a great deal of space in which to operate.
Ideally, there should be a method of applying a segmented code which can be quickly and accurately implemented within a limited space while being both human and machine-readable.